Method for preparing colorless fresh wolfberry fruit juice based on cooperation of electric flocculation and resin decoloration

Abstract

The invention discloses a method for preparing colorless fresh Chinese wolfberry fruit juice based on cooperation of electric flocculation and resin decoloration. The method comprises the following steps: (1) juice taking: cleaning fresh Chinese wolfberry fruits, squeezing, and filtering with a screen to obtain crude fruit juice; (2) electric flocculation clarification: putting the crude fruit juice into a flocculation electrolytic cell for electric flocculation, and separating flocs through a tubular centrifuge to obtain clarified fruit juice; (3) metal ion removal: enabling the flocculated clarified fruit juice to pass through weak acid type cation exchange resin to remove metal ions introduced by electric flocculation; (4) resin decoloration: enabling the fruit juice without metal ions to pass through decoloration macroporous resin, and collecting effluent, so as to obtain colorless and clear fresh Chinese wolfberry fruit juice; the method is simple and easy to implement, and the obtained fresh wolfberry fruit juice is colorless, transparent, good in clarity and high in polysaccharide content, can be used as a food raw material of beverages, alcoholic beverages, liqueur and the like, and is good in compatibility with common food base materials and excellent in stability.

Description

Technical Field

[0001] This invention relates to the field of fresh wolfberry juice refining technology, and in particular to a method for preparing colorless fresh wolfberry juice based on electrocoagulation and resin decolorization. Background Technology

[0002] Goji berries, a traditional Chinese medicinal and edible plant, are rich in polysaccharides, carotenoids, betaine, and other bioactive components, possessing various physiological functions such as antioxidation and immune regulation. In recent years, with the rapid development of the health food market, the market demand for fresh goji berry juice, as a highly nutritious health beverage, has continued to grow. However, due to the instability of macromolecules such as proteins, pectin, and polysaccharides, as well as natural pigments in goji berries, fresh goji berry juice is prone to technical problems during production, including turbidity, sedimentation, excessively dark color, and instability. This seriously affects the sensory quality and shelf life of the product. Furthermore, when used as an ingredient in other beverage processing, fresh goji berry juice affects the color and clarity of the product, limiting its application range. Summary of the Invention

[0003] The purpose of this invention is to address the problem that the fresh goji berry juice prepared in the current industry is cloudy and orange-red or dark red in color. As a beverage, it is prone to sedimentation during its shelf life, affecting its taste. As a food ingredient, it affects its application in colorless or light-colored liquid foods. The invention provides a method and product for preparing colorless and clear fresh goji berry juice based on electrocoagulation and resin decolorization.

[0004] In a first aspect, the present invention provides a method for preparing colorless fresh wolfberry juice based on electrocoagulation synergistic resin decolorization, comprising the following steps:

[0005] (1) Juice extraction: Wash the fresh wolfberries, press them, and filter them through a sieve to obtain crude juice; (2) Electrocoagulation clarification: The crude fruit juice is placed in a flocculation electrolysis tank for electrocoagulation, and the flocs are separated by a tubular centrifuge to obtain clarified fruit juice; (3) Metal ion removal: The clarified fruit juice after flocculation is passed through a weak acid cation exchange resin to remove the metal ions introduced by electrocoagulation; (4) Resin decolorization: The demetallized fruit juice is passed through a decolorizing macroporous resin and the effluent is collected to obtain colorless and clear fresh wolfberry juice.

[0006] Preferably, in step (1), the juice extraction method for fresh wolfberry is pressing, with a juice yield of 45%-65%, and the coarse filtration screen is 80-100 mesh.

[0007] Preferably, in step (2), the electrocoagulation equipment uses aluminum or iron plates as electrodes, with a DC voltage of 15-30V, a current density of 30-45mA / cm², a plate spacing of 2-3cm, and a processing time of 20-40min.

[0008] Preferably, in step (2), after electrocoagulation is completed, the settling time is 60-120 min and the speed of the tubular centrifuge is 8000-12000 r / min.

[0009] Preferably, in step (3), the ratio of the amount of juice to be demineralized to the resin is 3-5 ml / g, the flow rate is 0.5 bv / h-1.5 bv / h, and the ion exchange resin used is a weak acid cation exchange resin.

[0010] Preferably, in step (3), the cation exchange resin is pretreated with 5%-8% citric acid solution and washed with water until neutral before use.

[0011] Preferably, in step (4), the decolorizing macroporous resin used is an amine chelating resin (e.g., Xi'an Lanxiao LX-9E resin or similar resin).

[0012] Preferably, in step (4), the ratio of the juice to be decolorized to the resin is 4.0 ml / g-8.0 ml / g, and the flow rate is 1.0 bv / h-2.0 bv / h.

[0013] Secondly, the present invention provides colorless fresh wolfberry juice prepared by the above method.

[0014] Preferably, the obtained fresh wolfberry juice is colorless and transparent, with a wolfberry polysaccharide content of 7000mg / L-10000mg / L, a platinum-cobalt color of 6.5-9.50 Hazen, and a turbidity value of 0.500-0.950 NTU.

[0015] The principle of this invention is as follows: Metal cations dissolved from a metal anode hydrolyze in water to generate a series of mononuclear or polynuclear hydroxyl complexes, which form flocs with pectin, protein, and other substances in fresh goji berry juice. After physically removing the flocs, excess metal ions in the juice are replaced with cation exchange resin, and the juice is decolorized with amine chelating resin, thus obtaining colorless, clear, and transparent fresh goji berry juice. The specific principle is explained as follows: The turbidity of fresh goji berry juice is a manifestation of a complex and stable colloidal system formed by various natural macromolecules and microparticles, including pectin, protein, and polyphenols. These components interact, making the juice difficult to clarify under natural conditions. The electrocoagulation device dissolves and releases positively charged metal cations and polynuclear hydroxyl complexes formed by these metal cations in the fresh juice. Pectin, as a negatively charged polysaccharide (galacturonic acid polymer), readily reacts with Fe... 3+ Or Al 3+When complexation or charge neutralization occurs, the hydrophilic colloidal structure is disrupted, leading to aggregation. Proteins often carry a negative charge in acidic to neutral environments such as fruit juice, and aggregate through complexation with metal ions (such as Fe). 3+ Or Al 3+ Combined with carboxyl or amino groups, denatured aggregates, etc., are encapsulated in flocs. Simultaneously, the formed metal ion colloids can adsorb and encapsulate these unstable particles, forming large flocs that facilitate subsequent separation. However, electrocoagulation introduces excessive Fe... 3+ Or Al 3+ Excess metal cations are removed by adsorbing them using cation exchange resins. The main coloring substances in fresh wolfberry juice are carotenoids and chlorophyll. By utilizing the large surface area and hydrophobic framework inside the amine chelating macroporous resin, nonpolar van der Waals forces are generated with the aforementioned strongly hydrophobic (lipophilic) pigment molecules, thereby firmly adsorbing the pigments into the resin micropores and achieving juice decolorization.

[0016] This invention employs electrocoagulation combined with resin decolorization technology. It utilizes the principle of charge neutralization to flocculate and precipitate the protein and pectin components in fresh wolfberry juice, facilitating their physical removal. Then, ion exchange resin is used to remove excess metal cations introduced by electrocoagulation. Finally, decolorizing resin is used to remove the coloring substances in the juice, thereby solving the problem of cloudy and dark-colored fresh wolfberry juice.

[0017] The advantages of this invention over the prior art are: 1. Electrocoagulation combined with resin decolorization does not use organic solvents or chemical flocculants and is simple to operate. In traditional goji berry juice processing, the removal of pectin and protein mostly relies on enzymatic hydrolysis (such as pectinase) or chemical flocculants (such as gelatin and tannic acid), but this has problems such as long enzymatic hydrolysis time, risk of chemical residues, and loss of nutrients. Existing patents disclose membrane filtration decolorization technology, but the problems of decreased efficiency and high cost due to membrane fouling are prominent; other technologies use activated carbon adsorption decolorization, but it easily adsorbs flavor substances and cannot simultaneously remove metal ions.

[0018] 2. Electrocoagulation combined with resin decolorization can effectively remove introduced exogenous substances. Electrocoagulation technology, as a green physicochemical method, has been applied in wastewater treatment, but its potential in fruit juice clarification has not been fully explored, especially its highly efficient decolloid-breaking effect on the pectin-protein complex of wolfberry, which has not been reported. Furthermore, electrocoagulation may introduce metal ions (such as Al³⁺). + / Fe³ + The lack of a specific solution in existing technologies raises concerns about the safety of fruit juice. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain. If any definition stated in this section is contrary to or otherwise inconsistent with a definition stated in a patent, patent application, published patent application, or other publication incorporated herein by reference, the definitions listed here shall prevail over those incorporated herein by reference.

[0021] Unless otherwise specified, the methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials, reagents, and instruments used are conventional materials, reagents, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0022] Example 1 This embodiment provides a method for preparing colorless fresh wolfberry juice based on electrocoagulation and resin decolorization, including the following steps: (1) Juice extraction: Weigh 100kg of fresh wolfberry fruit, wash it clean, press it with a screw press to extract the juice, and filter it through a 50-mesh sieve to obtain 56.2L of crude juice; (2) Electrocoagulation clarification: The crude fruit juice is placed in the flocculation electrolysis tank for electrocoagulation. The electrocoagulation equipment uses aluminum plates as electrodes, DC voltage 15V, current density 35mA / cm², plate spacing 2cm, and processing time 20min.

[0023] After flocculation, the mixture was allowed to stand for 60 minutes, and then the flocs were removed using a tubular centrifuge to obtain a clear juice. The centrifuge speed was 8000 r / min. (3) Removal of metal ions: The clarified juice from the previous step is passed through an ion exchange resin. The ratio of juice to resin is 3 ml / g, the flow rate is 0.5 bv / h, and the ion exchange resin used is LXP-13 type cation exchange resin to obtain metal ion-free juice.

[0024] (4) Decolorization: The juice after removing metal ions was passed through LX-9E decolorizing macroporous resin. The ratio of decolorized juice to resin was 4.0 ml / g, the flow rate was 1.0 bv / h, and 51.1 L of colorless and clear wolfberry juice was obtained. The wolfberry polysaccharide content was 8434.41 mg / L, the aluminum ion content was 0.054 mg / L, the platinum cobalt color was 8.92 Hazen, and the turbidity value was 0.868 NTU.

[0025] According to the test, the colorless and clear wolfberry juice obtained in step (4) of this embodiment has a 98.15% lower platinum-cobalt color than that in step (1), and a 99.95% lower turbidity value than that in step (1).

[0026] The specific process for comparing the color and turbidity of fresh wolfberry juice and decolorized fresh wolfberry juice in this embodiment is as follows: I. The bitterness value of the low-bitterness kudzu root extract prepared in this embodiment was determined using an electronic tongue, and the results are as follows.

[0027] 1. Determination of Platinum-Cobalt Colorimetry in Fresh Goji Berry Juice in Example 1 Take appropriate amounts of the decolorized fresh wolfberry juice obtained in step (4) and the crude wolfberry juice obtained in step (1), and pour the two samples into cuvettes of the Hangzhou Caipu CS-820N benchtop spectrophotometer, and then place them on the analysis device. Before the sample measurement, the colorimetric system needs to complete initialization, self-test, calibration with pure water, and standard sample determination. After the measurement, rinse the cuvettes with pure water. Each sample is tested 4 times, and the data from the last 3 times are taken and the average value is calculated. The measurement results are shown in Table 1 below: Table 1. Results of Platinum-Cobalt Colorimetry Detection for Decolorized Fresh Goji Berry Juice and Crude Fresh Goji Berry Juice

[0028] 2. Turbidity Measurement Take appropriate amounts of the decolorized fresh wolfberry juice obtained in step (4) and the crude wolfberry juice obtained in step (1), and pour the two samples into the turbidity bottles of the Leici WZS-188E turbidity meter, and then place them into the turbidity meter. Before the sample measurement, the turbidity meter needs to complete the following steps: preheating for more than 30 minutes, self-testing, zero-point calibration with pure water, and calibration with various turbidity standard solutions. After the measurement, rinse the turbidity bottle with pure water. Each sample is tested 4 times, and the data from the last 3 times are taken and the average value is calculated. The measurement results are shown in Table 1 below: Table 2. Turbidity test results of decolorized fresh wolfberry juice and crude fresh wolfberry juice.

[0029] The experimental results in Tables 1 and 2 show that the decolorized fresh wolfberry juice obtained in step (4) of this embodiment has the characteristics of lighter color and lower turbidity compared with the crude fresh wolfberry juice in step (1).

[0030] Example 2 This embodiment provides a method for preparing colorless fresh wolfberry juice based on electrocoagulation and resin decolorization, including the following steps: (1) Juice extraction: Weigh 150kg of fresh wolfberry fruit, wash it clean, press it with a screw press to extract the juice, and filter it through an 80-mesh sieve to obtain 76.4L of crude juice; (2) Electrocoagulation clarification: The crude fruit juice is placed in the flocculation electrolysis tank for electrocoagulation. The electrocoagulation equipment uses iron plates as electrodes, DC voltage 30V, current density 45mA / cm², electrode spacing 3cm, and processing time 40min.

[0031] After flocculation, the mixture was allowed to stand for 120 minutes. Then, a tubular centrifuge was used to remove the flocs and obtain a clear juice solution. The centrifuge speed was 12000 r / min. (3) Removal of metal ions: The clarified juice from the previous step is passed through an ion exchange resin. The ratio of juice to resin is 5 ml / g, and the flow rate is 1.5 bv / h. The ion exchange resin used is a weak acid cation exchange resin. The resin is pretreated with 8% citric acid solution before use to obtain juice with metal ions removed.

[0032] (4) Decolorization: The juice after removing metal ions was passed through a decolorizing macroporous resin. The decolorizing resin used was an amino chelating resin (such as Xi'an Lanxiao LX-9E resin or a similar resin). The ratio of the juice to be decolorized to the resin was 8.0 ml / g, and the flow rate was 2.0 bv / h. 70.2 L of colorless and clear wolfberry juice was obtained. The wolfberry polysaccharide content was 8844.56 mg / L, the iron ion content was 0.013 mg / L, the platinum cobalt color was 7.84 Hazen, and the turbidity value was 0.835 NTU.

[0033] According to the test, the colorless and clear wolfberry juice obtained in step (4) of this embodiment has a 98.48% lower platinum-cobalt color than that in step (1), and a 99.89% lower turbidity value than that in step (1).

[0034] Example 3 This embodiment provides a method for preparing colorless fresh wolfberry juice based on electrocoagulation and resin decolorization, including the following steps: (1) Juice extraction: Weigh 80kg of fresh wolfberry fruit, wash it clean, press it with a screw press to extract the juice, and filter it through a 60-mesh sieve to obtain 44.6L of crude juice; (2) Electrocoagulation clarification: The crude fruit juice is placed in the flocculation electrolysis tank for electrocoagulation. The electrocoagulation equipment uses aluminum plates as electrodes, DC voltage 25V, current density 35mA / cm², plate spacing 2.5cm, and processing time 30min.

[0035] After flocculation, the mixture was allowed to stand for 100 minutes, and then the flocs were removed using a tubular centrifuge to obtain a clear juice. The centrifuge speed was 10,000 r / min. (3) Removal of metal ions: The clarified juice from the previous step is passed through an ion exchange resin. The ratio of juice to resin is 4 ml / g, and the flow rate is 1.0 bv / h. The ion exchange resin used is a weak acid cation exchange resin. The resin is pretreated with 6% citric acid solution before use to obtain juice with metal ions removed.

[0036] (4) Decolorization: The juice after metal ion removal is passed through a decolorizing macroporous resin. The decolorizing resin used is an amino chelating resin (such as Xi'an Lanxiao LX-9E resin or a similar resin). The ratio of juice to resin to be decolorized is 6.0 ml / g, the flow rate is 1.5 bv / h, and 40.1 L of colorless and clear wolfberry juice is obtained. The wolfberry polysaccharide content is 8395.75 mg / L, the aluminum ion content is 0.036 mg / L, the platinum cobalt color is 7.34 Hazen, and the turbidity value is 0.778 NTU.

[0037] According to the test, the colorless and clear wolfberry juice obtained in step (4) of this embodiment has a 99.17% lower platinum-cobalt color than that in step (1), and a 99.92% lower turbidity value than that in step (1).

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing colorless fresh wolfberry juice based on electrocoagulation and synergistic resin decolorization, characterized in that, Includes the following steps: (1) Juice extraction: Wash the fresh wolfberries, press them, and filter them through a sieve to obtain crude juice; (2) Electrocoagulation clarification: The crude fruit juice is placed in a flocculation electrolysis tank for electrocoagulation, and the flocs are separated by a centrifuge to obtain clarified fruit juice; (3) Metal ion removal: The clarified juice from the previous step is passed through an ion exchange resin to obtain metal ion-free juice; (4) Decolorization: The juice after removing metal ions is passed through a decolorizing macroporous resin to obtain colorless and clear fresh wolfberry juice.

2. The method according to claim 1, characterized in that: In step (1), fresh wolfberries are juiced using a screw juicer with a juice yield of 45%-65% and a sieve mesh size of 50-80.

3. The method according to claim 1, characterized in that: In step (2), the electrocoagulation equipment uses aluminum or iron plates as electrodes, with a DC voltage of 15-30V, a current density of 35-45mA / cm², a plate spacing of 2-3cm, and a processing time of 20-40min.

4. The method according to claim 1, characterized in that: In step (2), after electrocoagulation, the settling time is 60-120 min, and the flocs are removed by a tubular centrifuge to obtain the juice clear liquid. The centrifuge speed is 8000-12000 r / min.

5. The method according to claim 1, characterized in that: In step (3), the clarified juice is passed through an ion exchange resin to obtain a demetallized juice. The amount of resin used is 3ml / g-5ml / g, and the flow rate is 0.5bv / h-1.5bv / h.

6. The method according to claim 5, characterized in that: In step (3), the ion exchange resin used is a weak acid cation exchange resin. Before use, the resin is pretreated with 5%-8% citric acid solution and washed with water until neutral.

7. The method according to claim 1, characterized in that: In step (4), the juice after metal ions have been removed is passed through a decolorizing macroporous resin to obtain colorless and clear fresh wolfberry juice. The ratio of the decolorized juice to the resin is 4.0 ml / g-8.0 ml / g, and the flow rate is 1.0 bv / h-2.0 bv / h.

8. The method according to claim 1, characterized in that: In step (4), the decolorizing resin used is an amino chelating resin.

9. A colorless, clear fresh wolfberry juice prepared by the method according to any one of claims 1-8, characterized in that: The colorless and clear fresh wolfberry juice contains 7000mg / L-10000mg / L of wolfberry polysaccharides, has a platinum-cobalt color of 6.5-9.50 Hazen, and a turbidity of 0.500-0.950 NTU.

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